A tandem type color printer is known as an electro-photographic type color printer in which a plurality of photosensitive drums corresponding to colors of yellow, magenta, cyan and black are juxtaposed or arrayed side by side. Japanese Patent Application Publication No. 2009-210630 discloses such a color printer having a drum unit holding the four photosensitive drums and detachable from and attachable to a main casing. The drum unit includes a pair of side plates supporting each photosensitive drum therebetween and spaced away from each other in an axial direction of each photosensitive drum, the axial direction being rightward/leftward or lateral direction of the printer. Each drum body of each photosensitive drum is pressed by each developing roller.
A fitting member is fitted with each lateral end portion of each photosensitive drum such that the fitting member is not rotatable relative to the photosensitive drum. Each side plate is formed with drum support holes, and each photosensitive drum is rotatably supported to each drum support hole through a bearing member that is fitted over the fitting member. Driving force from the main casing is applied to each left end portion of each left side fitting member for driving each photosensitive drum.
More specifically, the fitting member has a laterally inner end portion inserted into a drum body of the photosensitive drum, and has a laterally outer end portion rotatably supported to the drum support hole through the bearing member. That is, in the fitting member, a portion inserted into the drum body is distant from a portion supported by the bearing member in the lateral direction, i.e., these two portions are different from each other in the lateral direction.